Acetabular Fracture

Introduction

Acetabular fractures are typically high-energy injuries and are often associated with insults to other major organ systems (up to 50%).  Fractures of the acetabulum may occur with or without disruption of the pelvic ring. 
Historically, these injuries were treated non-operatively due to the complexity of the fracture and difficult surgical exposure. Letournel and Tile are widely considered to be the fathers of modern osteosynthesis of the pelvis and acetabulum. Recent authors have also improved our understanding of these potentially debilitating injuries.  

Anatomy 

The bony anatomy of the pelvis and acetabulum is extraordinarily complex, and a better understanding is generally obtained with the use of a sawbones model or cadaver specimen.
The pelvis is made up of two innominate bones, and the sacrum. There is no inherent bony stability of the pelvis , but rather the pelvis is held together by an intricate system of ligaments. (For more on Pelvic anatomy, see Pelvic Fractures)
The anterior column (iliopectineal on AP radiograph) includes the anterior wall of the acetabulum, the anterior ilium, and the superior pubic ramus, while the posterior (ilioischial line on AP radiograph) column includes the posterior wall, and the ischium from the greater sciatic notch to the ischial tuberosity.  

Classification 

The classification of acetabular fractures was first published by Judet in 1964, and was modified by Letournel in 1981. There are 5 simple and 5 associated types of acetabular fractures, for a total of 10 types.  

Simple Fracture Patterns
Posterior Wall
Posterior Column 

Anterior Wall
Anterior Column
Transverse

Associated Fracture Patterns
Posterior Column/Posterior Wall
T-Type 

Anterior Column/Posterior Hemi-transverse
Transverse Plus Posterior Wall
Both Column 

Presentation 

Patients often present with a history of high-energy trauma, most commonly an auto-related injury.  Acetabular fractures have a high incidence of concomitant injury to other major organ systems. 

Diagnosis 

Initial evaluation begins with inspection of the airway, breathing, circulation, along with a complete assessment of neurologic function, and environmental exposures (ABCDE) in accordance with American College of Surgeons Advanced Trauma Life Support. After life threatening injuries are addressed, a complete physical examination is performed from head-to-toe, including rectal examination, looking for evidence of associated open fractures of the pelvis.
Initial trauma radiographs include antero-posterior pelvis and chest views and lateral cervical spine view.  The majority of acetabular injuries are visualize on the AP view.  Additional views include the Judet views (45-degree pelvic tilt views), and inlet/outlet views.
Judet views allow for improved inspection of the columns and walls of the bony acetabulum. The obturator oblique view (injured side rotated toward xray beam--obturator foramen appear wide open) brings the iliopectineal line (density of the anterior column) and posterior wall shadow into view, while the iliac oblique view (injured side tilted away from xray beam) allows for inspection of the ilioischial line (posterior column density) and anterior wall.  Special radiographic signs to look for include the Gull Sign (lateral spike protruding from acetabulum) which signifies a posterior wall fracture and the Spur Sign (lateral continuation of the ilium that is seen as a spike above the acetabulum on an obturator view) which signifies an associated both column fracture.
The inlet radiograph demonstrates antero-posterior displacement of the pelvic ring. The outlet radiograph demonstrates supero-inferior displacement of the pelvis ring (also see Pevic Fractures). 
Computed tomography scans with 1-2mm sections, coronal and sagittal reconstructions, and 3D views also allow for improved visualization and assessment of the fracture.
 

Treatment 

Closed reduction of an associated hip dislocation should be performed as soon as the patient's condition will allow appropriate sedation and muscle relaxation. If an associated femoral neck fracture is discovered on initial plain radiographs, open reduction is suggested in order to avoid displacement of an otherwise non-displaced fracture. 

Surgical Approaches 

Acetabular fractures should be exposed to allow the surgeon to address the area of maximal displacement. Thus, if the major displacement occurs posteriorly, posterior approaches should be used, while anterior displacement should be addressed utilizing approaches that expose anteriorly.  

Kocher Langenbeck. This approach is used for displaced posterior column, posterior wall, and transverse fractures that have the largest amount displacement posteriorly. Anterior wall and anterior column fractures cannot be reduced through a Kocher-Langenbeck approach.
 The patient is placed in the lateral decubitus position, or prone. The incision is centered over the greater trochanter and extends proximally toward the posterior superior iliac spine, and distally over the shaft of the femur. The interval splits the gluteus maximus proximally, and the tensor fascia distally. The short external rotators are taken down, with care to protect the sciatic nerve. The quadratus femoris muscle is the inferior limit of the exposure around the proximal femur, to avoid injuring the blood supply to the femoral head, the medial circumflex artery. Proximally, the inferior aspect of the greater sciatic notch is used as a landmark to avoid injuring the superior gluteal artery, which, if severed can retract into the pelvis and bleed profusely. If this occurs, the patient should immediately be placed in the supine position, and direct hemostasis should be obtained.  

Ilioinguinal. This approach exposes  the anterior column, pelvic brim, quadrilateral surface, anterior SI joint and inner table of the ilium. The patient is supine on a radiolucent or fracture table with the hip flexed 20 degrees to relax the hip flexors.
The incision begins 3-4 cm superior to the pubic crest and runs superior parallel to the iliac crest. The inner table of the ilium is dissected subperiosteally to the SI joint. The external oblique aponeurosis is opened and the floor of the inguinal canal is incised, after protecting its contents (spermatic cord in males, round ligament in females). The ilioinguinal and lateral femoral cutaneous nerves are protected. The lacuna vasorum (containing the large iliac vessels) and lacuna musculorum (containing the iliopsoas and femoral nerve) are separated by the iliopectineal fascia. This fascia is separated, and the true and false pelves are connected. The three windows of the exposure are thus defined: the lateral window (exposes the iliac fossa, the SI joint and superior ilium); the middle window (exposes the quadrilateral plate and lateral pelvic brim); and the medial window (exposes the medial iliopectineal line and pubis).  

Extended Iliofemoral Approach. This approach is rarely indicated. It is associated with a high incidence of heterotopic ossification. It is useful for displaced both column fractures, and T-Type fractures with displacement both anteriorly and posteriorly.
Exposure is similar to KL approach, with added trochanteric osteotomy and elevation of the gluteus medius from the outer table of the ilium to expose the anterior column.  

Complications 

Post-traumatic arthritis. In patients with an anatomic reduction of the articular surface, the incidence of post-traumatic arthritis is 10.2%, while the risk climbs to 35.7% in those patients with an imperfect reduction. 

Avascular necrosis of the femoral head. The risk is estimated to be approximately 3.1 percent.  

Infection. Letournel, et.al. (1993) reported 13/262 patients with wound complications, 5 extra-articular and 8 intra-articular.  

Neurologic Injury. Letournel, et.al. (1993) reported 9/262 patient with neurologic injury, most commonly involving the peroneal division of the sciatic nerve. 12.5% of patients had a preoperative deficit. 

Heterotopic Ossification. The risk is highest (35%) in patients undergoing an extended iliofemoral approach. The risk for the KL and Ilioinguinal approaches is 11% and 1% respectively. Prophylaxis is recommended with either indomethacin or perioperative radiation.